The present invention relates to a track jump controller and a track jump method, and in particular to a track jump controller and a track jump method that cause a pickup to jump by the number of target tracks in the track traverse direction by using for example a tracking actuator-driver then apply a braking pulse to stop the pickup.
An example of this type of related art track jump apparatus is disclosed in the Unexamined Japanese Patent Application Publication No. Hei9-102135 [G11B 7/19, G11B 7/085] published on Apr. 15, 1997. In the control circuit of this optical disk apparatus, a braking pulse is output when the lens reaches the position one track before the target track in terminating the seek operation. The control circuit detects the zero crossing cycle of a tracking error signal when the lens reaches a half track before the target track and corrects the magnitude or width of the braking pulse to reach the target track.
Another example of track jump apparatus is disclosed in the Unexamined Japanese Patent Application Publication No. 2000-353324 [G11B 7/085] published on Dec. 19, 2000. In the optical recording/playback apparatus, the travel time to a point in the light beam during jump is measured in the course of focus jumping and the waveform of the deceleration pulse is changed to drive the tracking actuator. After a deceleration signal is output, the travel means is forcibly driven until the level of the tracking error signal drops below the predetermined value. This is provided a stable focus jumping performance with respect to disturbance caused by vibration on the apparatus or partial eccentricity of an optical disk, thereby assuring high-speed playback and recording.
According to such related art technologies, in the former case, a table having the magnitude (level) or width of a braking pulse corresponding to the zero crossing cycle is required. This leads to increased memory capacity. In case eccentricity of the disk is present, as shown in FIG. 10, the disk speed is temporarily greater than the travel speed of the pickup from end of braking to reaching the target track. This reverses the travel direction of the pickup with respect to the disk at the point indicated as P thus causing a tracking fault. That is, the pickup is uncontrollable and as a result, the track is not reached. In such a fault, jump must be retried from the start thus taking time before playback starts.
In the latter case, the travel time is measured during acceleration or a deceleration pulse is calculated from the measured time thus complicating the processing. The pickup is forcibly moved by using the travel means immediately after the output of a deceleration signal to retain the level of the tracking error signal below the predetermined value. The pickup is thus forcibly moved by the travel means even in case the travel direction of the pickup with respect to the disk is the same, which is needless control.
Thus, the main object of the invention is to provide a track jump controller for disk apparatus and a track jump method effective for a tracking fault caused by an eccentric disk.
The first aspect of the invention is a track jump controller for disk apparatus that causes a pickup to jump by the number of target tracks in the track traverse direction by using a tracking actuator-driver then applies a braking pulse to stop the pickup, characterized in that a kick pulse of the polarity opposite to that of the braking pulse to a tracking actuator-driver when a tracking error signal does not drop below a predetermined value within a predetermined time shorter than the zero crossing cycle of the tracking error signal after the braking pulse is applied.
The second aspect of the invention is a track jump controller including a tracking actuator-driver for driving the pickup in the track traverse direction in track jump, braking pulse application means for applying a braking pulse to the tracking actuator-driver when the number of target tracks have been jumped over, determination means for determining whether a tracking error signal drops below a predetermined value within a predetermined time after the braking pulse is applied, and kick pulse application means for applying a kick pulse of the polarity opposite to that of the braking pulse to the driver when the determination means determines that the tracking error signal drops below the predetermined value.
The third aspect of the invention is a track jump method for disk apparatus that causes a pickup to jump by the number of target tracks in the track traverse direction by using a tracking actuator-driver then applies a braking pulse to stop the pickup, including the steps of (a) jumping over the number of target tracks, (b) applying a braking pulse, (c) determining a tracking error signal drops below a predetermined value within a predetermined time after the braking pulse is applied, and (d) outputting a kick pulse of the polarity opposite to that of the braking pulse when the tracking error signal drops below the predetermined value.
In the track jump controller, when a seek instruction such as fast forwarding, rewinding, selection of music or skipping of music is given during playback of a DVD or a CD, the total number of tracks to be jumped over is calculated based on the current pickup position and the target pickup position and jump is started. That is, the pickup is caused to jump by the number of target tracks (total number of tracks) in the track traverse direction by using a tracking actuator-driver, then a braking pulse is applied to stop the pickup. After the output (application) of the braking pulse is over, it is determined whether the tracking error signal drops below a predetermined value within a predetermined time shorter than the zero crossing cycle of the tracking error signal. In case the tracking error signal does not drop below the predetermined value, it is determined that the travel direction of the pickup or objective lens with respect to the disk is beginning to be reversed, and a kick pulse the polarity opposite to that of the braking pulse, or a correction kick pulse for acceleration in the jump direction, is applied to the tracking actuator-driver. Thus, it is possible to prematurely prevent reversal of the travel direction of the objective lens with respect to the disk.
According to the invention, a correction kick pulse is output based on the level of the tracking error signal at a predetermined time after braking is over in order to prematurely prevent the travel direction of the pickup with respect to the disk from being reversed. This allows the pickup to reach the target track successfully.
The aforementioned object of the invention, other objects, features and advantages will be clear from the detailed description of the following embodiment referring to drawings.